spark, fuel,compression..it has to run, I had a chop job wiring harness once that would disconnect the coil on start but be okay in run. doubt that's your problem. sounds like distributor is 180 out, or your timing marks are off. I rebuilt a chibby once,(and only) and cam geared it wrong. wouldn't run but it would fire. re-indexed gears and worked fine. I have been fooled with using finger method for distributor install. exhaust stroke was still strong, pull the valve cover to watch.